Mildew smell in house

[Scott W.]

I bought a house almost 10 years ago with an odor (yep, I had it inspected); people have described the smell as musty, an old dog smell, & an old house smell. When I was dating my wife, she'd go back to her place & her clothes would smell of it.

the house is a ranch on about a 2' dirt crawl with a vapor barrier (yeah, you REALLY gotta crawl).

When the wife moved in 5 years ago, she wanted the smell gone. We hired a company to dig a french drain/sump pump, install one of those black vapor barriers, & they then cemented it.

I've read different levels of opinion as to concrete or not to concrete a crawl.

Within days, the smell was nonexistent; people who had been over before had commented on the lack of smell.

The home is now a rental; I was doing some work on it last week, with my handyman, & we both commented on the smell; it's very minor, yet noticeable upon entry.

My concern is future tentants/homebuyers will be turned off by the smell. I'm at a loss for solutions. There is a furnace humidifier as well. I'm not sure if the tentants run it though & if it would even make a difference.

Any solutions/ideas?

[Ed O.]

Are you certain there's no new potential causes of moisture in the home? A leaky drain pipe, supply line, failed wax ring, or something like that?
Is the roof tight? You might check in the attic and see if there's any signs of water damage.
Does the shower have a fart fan and does it exhaust the air outside, not at all, or into the attic?
If the hvac is a forced air system, perhaps it may help to clean the duct work. Beware of the scummy contractors in this field.
New air filters may be the cheapest attempt, try a pleated one instead of a cheap rock catcher.
See if the problem gets better, worse, or if it changes as the weather does.
Is the crawl space vented? This might help.
Is rainwater entering the crawl? Is the yard pitched away from the home? Are the downspouts extended to get the rainwater a good distance from the house. I see it all the time, where they just dump water right at the corner of the home. This is a bad thing.

Good luck. Let me know if you get it.